Pressing a grand piano key moves a connected system of levers that propels a felt-covered hammer into one or more strings. The hammer then moves away so the strings can vibrate, while the damper lifts off the strings. Releasing the key generally allows the damper to return and silence the note, unless the sustain pedal is holding the dampers up.
A piano key is a lever, not a button connected directly to a string
The visible ivory-colored or black surface is only the front of a longer key lever. When your finger pushes the front down, the rear rises. That motion drives a mechanism collectively called the action. The action turns your controlled finger movement into a quick, repeatable hammer strike.
Follow the labeled parts in this grand-piano action
In the close-up below, the key is labeled A at the far right and the hammer is labeled F toward the left. Between them are parts that transfer and regulate movement. This is a real grand-piano double-escapement action, not an illustration of an electronic keyboard.
Why doesn’t the hammer stay against the string?
Near the top of the stroke, an escapement mechanism allows the hammer to continue moving briefly under its own momentum instead of being driven hard against the string. That matters because a hammer held against a string would choke its vibration. After contact the hammer rebounds and is caught or controlled by parts of the action.
How do grand pianos repeat notes quickly?
A modern grand action includes a repetition mechanism that helps prepare the hammer for another strike before the key has been completely released. Pianists still need controlled finger motion, but the mechanism makes fast repeated notes practical. Upright-piano actions work differently, so a cross-section of a grand should not be treated as a universal blueprint for all pianos.
What is the damper doing while you play?
For many notes, pressing the key also lifts a felt damper off the strings. When you let go, the damper returns and reduces the vibration. The right-hand sustain pedal holds dampers up so tones continue after the fingers leave the keys. The highest notes on many acoustic pianos do not have dampers, so their natural decay differs.
A simple listening exercise
On an acoustic piano, press and hold a middle-register key gently after sounding it; listen as the note fades. Release the key and notice the more abrupt stop. Then try the same note with the sustain pedal depressed. These three versions demonstrate the relationship among the hammer, vibrating string and damper. Do not reach into a moving piano action while someone plays.
Frequently asked questions
Does the key itself touch the strings?
No. In an acoustic grand piano, the action transfers the key’s movement to a hammer that strikes the strings.
Is a louder note caused by holding the key down harder?
The hammer’s speed at impact matters for loudness. Continued pressure after the hammer strikes does not keep adding sound energy to that strike.
Does a digital piano have this hammer mechanism?
Usually not in the same acoustic form. Digital instruments use sensors to detect key motion and produce an electronic sound, although some simulate the feel of a hammer action.
For a beginner’s approach, see how to play your first piano notes. Technical reference: Yamaha’s explanation of the piano action.
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